Apparatus and a method for in-vivo power generation

ABSTRACT

An apparatus for an in-vivo power generation comprises a fuel convertor for converting glucose in a fluid to a hydrogen rich, low carbon fuel such as ethanol or methanol by the action of a bioenzyme on the glucose in the CSF. The fluid can be any one of cerebrospinal fluid, urine and glucose solution. The apparatus further comprises a biofuel cell comprising a cathode chamber and an anode chamber with a membrane assembly sandwiched between them. The membrane assembly comprises a cathode, an anode and a proton exchange membrane. The cathode is coated with an enzyme laccase, which enables extraction of oxygen when the fluid is passed through the cathode chamber. The oxygen from the cathode chamber and the hydrogen in the hydrogen rich fuel from the anode chamber diffuses through the proton exchange membrane and reacts at an ionic level to result in water and electrical power.

RELATED APPLICATION

This application is a divisional of U.S. patent Ser. No. 14/280,341filed on May 16, 2014, which claims priority under 35 U.S.C. § 119 toIndian Patent Application No. 2808/MUM/2013, filed on Aug. 28, 2013. Theentire content of the foregoing applications are explicitly incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates generally to an apparatus and method forin-vivo power generation. More specifically, the present inventionrelates to a biofuel cell using a fluid rich in glucose for electricalpower generation.

BACKGROUND

The numbers of body implants have shown an exponential increase in theiruse. The traditional power sources used in the implants are lithium ionbutton batteries which need to be frequently recharged, and have a shortlifetime of 2 years to 3 years and to replace them a surgery is requiredevery time. These batteries also result in toxic contamination insidethe body and result in fatalities.

US 2006/0020239 A1 delineates a cerebrospinal fluid (CSF) flow sensingdevice for sensing CSF flow through an implantable ventricular shunt.The sensing device is implanted within the CSF shunt, and includes aflow sensor to sense flow rate or shunt blockage. The sensing device iseither placed within or adjacent the fluid path through the shunt. Thesensing device transmits and sends the flow rate to an externalmonitoring device by wireless telemetry. The sensing device may beintegrally formed as part of the shunt, or clamped onto apportion of theshunt, in which case the sensing device may be reusable. An externalmonitor receives the transmitted flow signal and presents informationbased on the flow signal. The disadvantage of the above described deviceis that the device has to be inductively powered or has to have its ownpower supply.

There is therefore a need to mitigate the disadvantages associated withthe devices explained above.

OBJECTIVE OF THE INVENTION

1. To achieve a power source which is biocompatible and used for in-vivoapplications in the human body.

2. To achieve a nano scale biofuel cell with high power output and highefficiency.

3. To achieve using glucose present in the cerebrospinal fluid, glucosesolution and urine for generation of electrical power.

SUMMARY

According to one aspect of the invention, there is disclosed anapparatus for in-vivo power generation. The apparatus comprises a fuelgenerator arranged to produce a hydrogen rich fuel from a fluid flowingthrough the fuel generator. The apparatus further comprises a biofuelcell comprising a first chamber and a second chamber separated by amembrane assembly, wherein a first electrode in the membrane assemblycomprises a catalyst for enabling extracting oxygen from the fluid, thefluid being configured to flow through the first chamber and wherein thesecond chamber is arranged to receive the hydrogen rich fuel from thefuel generator. Electrical power is generated when the oxygen from thefirst chamber and hydrogen in the hydrogen rich fuel from the secondchamber combine reactively.

According to another aspect of the invention, there is disclosed amethod for in-vivo power generation using an in-vivo power generationapparatus comprising a fuel generator and a biofuel cell, wherein thebiofuel cell comprises a first chamber and a second chamber and amembrane assembly disposed between the first chamber and the secondchamber. The disclosed method comprises generating a hydrogen rich fuelfrom a fluid by passing the fluid through the fuel generator. The methodfurther comprises extracting oxygen from the fluid by passing the fluidthrough the first chamber of the biofuel cell, wherein a catalyst in afirst electrode in the membrane assembly enables extracting oxygen fromthe fluid. The method further comprises passing the hydrogen rich fuelthrough the second chamber in the biofuel cell. The method furthercomprises generating electrical power by a reaction occurring across themembrane assembly in the biofuel cell, the reaction occurring betweenthe oxygen from the first chamber and hydrogen in the hydrogen rich fuelfrom the second chamber.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of an apparatus for in-vivo powergeneration;

FIG. 2 is a schematic illustration of a bio fuel cell of the apparatusfor in-vivo power generation of FIG. 1;

FIG. 3 is a flowchart showing the process steps for a method of in-vivopower generation in an in-vivo power generation apparatus;

FIG. 4 is a schematic showing a conditioning unit interfacing theapparatus for in-vivo power generation and the body implant;

FIG. 5 shows a step-up unit forming a component of the conditioning unitof FIG. 4;

FIG. 6 shows a boost convertor unit of the conditioning unit of FIG. 4;and

FIG. 7 shows a schematic of a transdermal glucose reservoir implanted inan epidermal layer of a user.

DETAILED DESCRIPTION

FIG. 1 is a schematic illustration of an apparatus 100 for in-vivo powergeneration. As illustrated in FIG. 1, the apparatus 100 for in-vivopower generation is used for powering medical implants inside humanbodies and animals. The apparatus 100 uses raw materials for powergeneration from inside human bodies and animals, as will be describedhereinafter.

The apparatus 100 comprises a fuel generator 10 and a biofuel cell 15.The fuel generator 10 is arranged to produce a hydrogen rich fuel from afluid flowing through the same. The fuel generator 10 can be a lowcarbon fuel convertor which is configured to receive the fluid andproduce the hydrogen rich fuel by the action of a bioenzyme on glucosein the fluid. The fluid that is fed and arranged to flow through thefuel generator 10 can be any one of cerebrospinal fluid (CSF), urine andglucose solution. CSF is a clear and colorless bodily fluid produced inthe choroid plexus of the brain. CSF contains glucose and the apparatus100 is arranged to use the glucose in the CSF to generate power. Theglucose in CSF is D-glucose and the concentration of D-glucose in CSF is400-850 mg/L. The fuel generator 10 is arranged to receive the CSFthrough a shunt tube 20 from a vessel in the human body that carriesCSF. The shunt is a passage which allows movement of any fluid from onepart of the body to another. The shunt tube 20 enables movement of CSFto the fuel generator 10. The shunt tube 20 can also be referred to as acerebral shunt as the shunt tube 20 carries CSF. In an embodiment thatuses urine as the fluid, the apparatus 100 is planted in proximity tothe urinary bladder or the ureter such that urine from the urinarybladder or urine flowing into the urinary bladder is diverted into theapparatus 100 for power generation. The urine is supplied to theapparatus 100 through the shunt tube 20 from the urinary bladder orureter. In this embodiment, the apparatus 100 utilizes the glucose inthe urine. In another embodiment, glucose solution is used as the fluidand is transferred by the shunt tube to the apparatus 100. The mechanismof infusing and transporting the glucose solution is describedhereinafter.

The apparatus 100 used with urine, glucose solution and CSF are the sameand the method of working is also the same, which is describedhereinafter. The apparatus 100 to be used with glucose solutioncomprises an additional component, which will be described hereinafter.

The low carbon fuel convertor which is the fuel generator 10 comprises abioenzyme, which can be any one of pectine methyl esterase (PME) andzymase (yeast). Enzymes are biological molecules responsible for amultitude of chemical interconversions that are important for biologicallife. Among many biological functions carried out by enzymes in humans,some of them are the digestion of food and synthesis of DNA. The actionof pectine methyl esterase on the fluid flowing through the fuelgenerator 10 yields methanol. The chemical formula of methanol is CH₃OH.It is apparent that methanol comprises 4 hydrogen atoms and 1 carbonatom. The hydrogen-carbon ratio which is depicted by H/C ratio is 4:1for methanol. The action of zymase on the fluid flowing through the fuelgenerator 10 yields ethanol. The chemical formula of ethanol is C₂H₅OH.The reaction that occurs in the fuel generator 10 to convert glucose toethanol using zymase is as follows:

It is apparent that ethanol comprises 6 hydrogen atoms and 2 carbonatoms. The H/C ratio for ethanol is 6:2. It is apparent that both inethanol and methanol, the hydrogen content is greater than the carboncontent and that forms the reason for ethanol and methanol to bereferred to as a hydrogen rich fuel or a low carbon fuel.

FIG. 2 is a schematic illustration of a biofuel cell of the apparatus100. As illustrated in FIG. 2, the biofuel cell 15 comprises a firstchamber 25 and a second chamber 30, separated by a membrane assembly 35.The first chamber 25 is a cathode chamber. The second chamber 30 is ananode chamber. The first chamber 25 comprises a first chamber entrance26 and a first chamber exit 27. As illustrated in FIG. 1, a tube 40departs from the shunt tube 20 carrying the fluid directly to the firstchamber entrance 26 of the first chamber 25 of the biofuel cell 15. Theshunt tube 20 is composed of silicone material. The tube 40 can also bereferred to as a cathode chamber nanochannel.

The second chamber 30 or the anode chamber is arranged to receive thehydrogen rich fuel from the fuel generator 10 through a second chamberentrance 31. The hydrogen rich fuel is transported from the fuelgenerator 10 to the second chamber 30 through an anode chambernanochannel 45 as illustrated in FIG. 1. As illustrated in FIG. 2, themembrane assembly 35 is an assembly comprising a first electrode 36, asecond electrode 37 and a membrane 38. The first electrode 36 is aporous gas diffusion electrode (cathode) 36 and the second electrode 37is a porous gas diffusion electrode (anode). The membrane 38 is a protonexchange membrane. The porous gas diffusion electrode (cathode) 36 canalso be referred to as a cathode 36 for the purposes of explanation. Theporous gas diffusion electrode (anode) 37 can also be referred to as ananode 37 for the purposes of explanation. The proton exchange membrane38 can also be referred to as a polymer electrolyte membrane and is asemipermeable membrane, which is understood by a person skilled in theart. The proton exchange membrane 38 is disposed between the cathode 36and the anode 37 forming a sandwich like structure. The proton exchangemembrane comprises nafion, which is a sulfonated tetrafluoroethylenebased fluoropolymer-copolymer. Nafion is used as a proton conductor inthe proton exchange membrane. As described above, the cathode 36 and theanode 37 form part of the membrane assembly 35. The cathode 36 is opento a cavity (not shown in Figures) of the cathode chamber 25 and theanode 37 is open to a cavity (not shown in Figures) of the anode chamber30. Both the cathode 36 and the anode 37 are made of Raney-platinumfilm. The cathode 36 is coated with a catalyst, which is capable ofextracting oxygen from the fluid, when the fluid flows through thecavity of the first chamber 25. The fluid enters the first chamber 25through the first chamber entrance 26 and as the fluid flows along thefirst chamber 25, oxygen is extracted from the fluid by the action ofthe catalyst laccase coated on the cathode. The oxygen generated in thefirst chamber 25 and the hydrogen from the hydrogen rich fuel in thesecond chamber 30 combine reactively across the membrane assembly 35 toresult in a flow of electrons resulting in electricity. To elaborate,firstly the hydrogen ionizes and then diffuses through the protonexchange membrane 38 to combine with oxygen to form water. The half-cellreactions taking place are:

Anode: H₂+O⁻²→H₂O+2e⁻

Cathode: ½O₂+2e⁻→O⁻²

Overall: H₂+½O₂→H₂O

In the anode chamber 30, electrons are stripped from the hydrogen atomsat the anode 37. The positively charged hydrogen ions (protons) thenpass through the proton exchange membrane 38 to the cathode 36, wherethey react with the oxygen and the stripped electrons to form water. Theflow of electrons from the anode 37 to the cathode 36 results inelectrical power to be supplied to in-vivo devices.

As illustrated in FIG. 2, the biofuel cell 15 is elongated with thefirst chamber 25, the second chamber 30 and the membrane assembly 35between the first chamber 25 and the second chamber 30 being elongated.The first chamber entrance 26 and the second chamber entrance 31 aredisposed at opposite ends of the biofuel cell 15, such that the fluidentering the first chamber entrance 26 and flowing through the firstchamber 25 and the hydrogen rich fuel entering the second chamberentrance 31 and flowing through the second chamber 30 flow in oppositedirections in the biofuel cell 15. As illustrated in FIG. 1, the fluidflowing out from the first chamber 25 and from which oxygen has beenextracted flows out through a first nanochannel 50 to an exitnanochannel 55 through an intermediate nanochannel 60. The compositionalremnants of the fluid from which hydrogen rich fuel has been generatedin the fuel generator 10 passes to the exit nanochannel 55 through asecond nanochannel 65. The compositional remnants of the hydrogen richfuel from which hydrogen is extracted in the second chamber 30 alongwith water flows out through a third nanochannel 70. The thirdnanochannel 70 connects to the intermediate nanochannel 60 and drainsinto the intermediate nanochannel 60. The second nanochannel 65 from thefuel generator 10 and the intermediate nanochannel 60 meet and form theexit nanochannel 55. The exit nanochannel 55 drains into the abdominalcavity of the human being inside which the apparatus 100 is implanted.

The spatial and positional orientation of the apparatus 100 asillustrated in FIG. 1 enables the fluid to flow through the fuelgenerator 10 to produce the hydrogen rich fuel and the hydrogen richfuel to flow through the second chamber 30 and the fluid directlythrough the first chamber 25 naturally aided by gravity, without thenecessity for any powered fluid pumps. The oxygen and hydrogen in thecathode chamber 25 and the anode chamber 30 which is in gaseous formwill be higher in volume when compared to the liquid form and willnaturally be driven to diffuse through the membrane assembly 35,therefore running the biofuel cell 15.

In an exemplary embodiment of the apparatus 100, a width and a height ofthe first chamber 25 and the second chamber 30 are 500 nm and 500 nmrespectively. A thickness of the cathode and the anode are 100 nm and100 nm respectively. A length of the first chamber 25, the secondchamber 30 and the membrane assembly 35 are 1000 nm, 1000 nm and 1000 nmrespectively. A thickness of the membrane 38 is 100 nm. It is thusapparent from the above that the biofuel cell 15 is a nano-scale deviceand can thus be effectively and conveniently implanted in the humanbody.

As illustrated in FIG. 1, the apparatus 100 further comprises apackaging 75, the packaging composed on a biocompatible material such asbio glass. The chemical formula for bio glass is Na₂O—CaO—SiO₂—P₂O₅. Thebio glass in the packaging 75 can be coated with polydimethysiloxane(PDMS). PDMS belongs to a group of polymeric organosilicon compounds.PDMS is optically clear, inert, non-toxic and non-flammable. PDMS isalso referred to as silicone. The above mentioned properties of PDMSenable PDMS to be coated on the packaging 75 which is implanted insidethe human body without any deleterious effects to the human body. Thepackaging and PDMS are hemocompatible and non-cytotoxic, in addition toexhibiting other biocompatible features. The bio glass packagingprovides sturdy support to the package. The coating of PDMS as describedabove provides protection for the bio glass packaging 75 from variousin-vivo forces. In other words, the coating of silicone reduces thebrittleness of the packaging 75. The bio compatible material is notlimited to what has been described above and can include other similarmaterials as well.

FIG. 3 is a flowchart showing the process steps for a method 200 ofin-vivo power generation using the in-vivo power generation apparatus100. As illustrated in FIG. 3, the method 200 comprises a step 210 ofgenerating the hydrogen rich fuel from the fluid by passing the fluidthrough the fuel generator 10, which has already been described earlier.The method 200 further comprises a step 220 of extracting oxygen fromthe fluid by passing the fluid through the first chamber 25 of thebiofuel cell 15. The first electrode in the membrane assembly 35 iscoated with a catalyst which enables extracting oxygen from the fluid. Afurther step 230 comprises passing the hydrogen rich fuel through thesecond chamber 30 in the biofuel cell 15. The method 200 comprises afurther step 240 which comprises generating power by a reactionoccurring across the membrane assembly 35, the membrane assembly 35separating the first chamber 25 and the second chamber 30. The reactionoccurs between the oxygen from the first chamber 25 and the hydrogen inthe hydrogen rich fuel from the second chamber 30. The step 210comprises utilizing a bioenzyme in the fuel generator 10 or the lowcarbon fuel convertor to act on glucose in the fluid to generate thehydrogen rich fuel, which can be one of ethanol and methanol.

The apparatus 100 for in-vivo power generation can be fabricated on achip which can be implanted in the human body. The lifetime of theapparatus 100 described above can be 40000 to 60000 hours.

The CSF that is used as the fluid in the apparatus 100 and the method200 can be any one of waste CSF and utilizable CSF. Waste CSF is CSFthat is being drained out from the cerebral region through the thoraxinto the abdomen of the human body or the animal after being utilized inthe cerebral region. Utilizable CSF is the CSF in the brain and which isstill being utilized in the cerebral region. The apparatus 100 andmethod 200 can be implanted and employed in any part of the human bodyand animal and therefore utilizes CSF that is waste CSF or utilizableCSF depending on the implanted location.

Moreover, the power generated by the fuel cell or apparatus 100 can beboosted or raised to be effectively utilized by the implant inside thebody. FIG. 4 is a schematic showing a conditioning unit 300 interfacingthe apparatus 100 for in-vivo power generation with the body implant.The power output generated by the above described fuel cell is in theorder of 3-8 μW. This level of power output is conditioned by theconditioning unit 300. The conditioning unit 300 is also referred to asan ultra-low power conditioning circuit or ultra-low power conditioningunit. The power conditioned by the conditioning unit 300 is supplied tothe body implant 400. The conditioning unit 300 comprises a step-up unit310, a boost convertor unit 320 and a control unit 330.

FIG. 5 shows the step-up unit 310. The step-up unit 310 comprises astep-up transformer 340 and a normally ON N-channel JFET transistor 350.Upon the apparatus 100 supplying the generated power to the step-up unit310, the current increases in the primary winding of the step-uptransformer 340. Consequently, the secondary winding applies a positivevoltage on the gate of the JFET. As the JFET gate-source PN junctionconducts, the output capacitor is charged with a negative voltage,thereby resulting in a negative output voltage. When the primary currentreaches saturation, the voltage across the primary winding cancels andthe negative voltage of the output capacitor is applied on the gate ofthe JFET pinching it off. The current in the primary winding decreasesand a negative voltage is applied by the secondary winding on the gateof the JFET, resulting in the switching off of the JFET. The negativevoltage falls back to zero and the oscillation process starts again. Anexample of JFET is 2N4338, which is characterized by a low gate-sourcecutoff voltage, which is from −0.5V to −1V. This characteristic of theJFET allows the boost convertor unit 320 to start-up with a small inputvoltage. The transformer turns-ratio is 1:20, which reflects a trade-offbetween efficiency and step-up ability.

FIG. 6 shows the boost convertor unit 320 of the conditioning unit 300of FIG. 4. The boost convertor 320 works on the principle of thetendency of an inductor to resist changes in current by creating anddestroying a magnetic field. The boost convertor 320 comprises aninductor 360, a switch 370, a diode 380 and a capacitor 390. In a boostconvertor, the output voltage is always higher than the input voltage.Upon closing the switch 370, current flows through the inductor 360 inclockwise direction and the inductor 360 stores some energy bygenerating a magnetic field. The polarity on the left side of theinductor in the circuit shown in FIG. 6 is positive. Upon opening theswitch 370, current reduces as the impedance is higher. The magneticfield previously created is destroyed to maintain the current flowtowards the load. The polarity is thus reversed. Consequently, twosources will be in series causing a higher voltage to charge thecapacitor through the diode 380. If the switch 370 is cycled fastenough, the inductor 360 will not discharge fully in between chargingstages, and the load will always see a voltage greater than that of theinput source alone when the switch 370 is opened. Also when the switch370 is opened, the capacitor 390 in parallel with the load is charged tothe combined voltage. Upon closing the switch 370 and the right side ofthe boost convertor circuit is shorted from the left side, the capacitor390 is therefore able to provide the voltage and energy to the load.During this time, the diode 380 prevents the capacitor 390 fromdischarging through the switch 370. Opening the switch 370 fast enoughprevents the capacitor 390 from discharging too much or a lot.

The control circuit 330 comprises an ultra-low power microprocessor suchas MSP-430 or anything similar. The control circuit 330 receivesinformation from the body implant 400 with regards to power requirement,duration and other such related things. The control circuit 330communicates with the boost convertor 320 to supply power to the implantwith the desired characteristics.

The advantage of the conditioning unit 300 is that the conditioning unitboosts or raises the low voltage power generated by the fuel cell to ahigher voltage level and also manages the power requirement anddistribution so as to be effectively utilized by the implant in thebody.

FIG. 7 shows a schematic of a transdermal glucose reservoir 500implanted in an epidermal layer of a user that uses the apparatus 100.As illustrated in FIG. 7, the skin shows epidermis 510 and dermis 520.The reservoir 500 is implanted on the epidermal layer 510. The reservoir500 can be connected to an external supply of glucose solution or can bearranged to store glucose solution temporarily. The reservoir 500comprises a plurality of micro needles 530 for delivery of glucosesolution to the shunt tube to be delivered to the apparatus 100. Theplurality of micro needles 530 empty the glucose solution to a trough540 which is connected to the shunt tube for transporting to theapparatus 100.

It is to be understood that the foregoing description is intended to bepurely illustrative of the principles of the disclosed techniques,rather than exhaustive thereof, and that changes and variations will beapparent to those skilled in the art, and that the present invention isnot intended to be limited other than as expressly set forth in thefollowing claims.

I claim:
 1. A method for in-vivo power generation using an in-vivo powergeneration apparatus comprising: a fuel generator and a bio fuel cell,wherein the biofuel cell comprises a first chamber and a second chamberand a membrane assembly disposed between the first chamber and thesecond chamber, the method comprising: generating a hydrogen rich fuelfrom a liquid by passing the liquid through the fuel generator whereinthe fuel generator is a low carbon fuel convertor which is configured toreceive the liquid and produce the hydrogen rich fuel by the action of abioenzyme on glucose in the liquid; extracting oxygen from the liquid bypassing the liquid through the first chamber of the bio fuel cell,wherein a catalyst in a first electrode in the membrane assembly enablesextracting oxygen from the liquid; passing the hydrogen rich fuelthrough the second chamber in the bio fuel cell; and generatingelectrical power by a reaction occurring across the membrane assembly inthe bio fuel cell, the reaction occurring between the oxygen andhydrogen in the hydrogen rich fuel, from the first chamber and thesecond chamber respectively.
 2. The method for in-vivo power generationas claimed in claim 1, wherein the liquid is one of cerebrospinal fluid,glucose solution and/or urine.
 3. The method for in-vivo powergeneration as claimed in claim 1, wherein the bioenzyme is one ofpectine methyl esterase or zymase.
 4. The method for in-vivo powergeneration as claimed in claim 1, wherein a quantity of hydrogen isgreater than a quantity of carbon in the hydrogen rich fuel.
 5. Themethod for in-vivo power generation as claimed in claim 4, wherein thehydrogen rich fuel is one of ethanol or methanol.
 6. The method forin-vivo power generation as claimed in claim 1, wherein the catalyst islaccase.
 7. The method for in-vivo power generation as claimed in claim1, wherein the membrane is nafion.
 8. The method for in-vivo powergeneration as claimed in claim 7, wherein the thickness of the membraneis 100 nm.